Radio signaling system



INVENTOR NEWSOME H.CLOUGH N. H. CLOUGH RADIO SIKGNALING SYSTEM Filed May29, 1936 n u n e n 1 n n 1 1 n 4 n c 14 l ATTORNEY FTW vvv

' April 18, 1939.

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Patented Apr. 1K8, 1939 RADIO SIGNALIN G SYSTEM Newsome Henry Clough,Brentwood, England, assignor to Radio Corporation of America, acorporation of Delaware Application May 29, 1936, Serial No. 82,515 InGreat Britain May 31, 1935 4 Claims. (Cl. Z50-36) f 'I'his inventionrelates to lelectric signaling systems suitable for use in radionavigation systems, and hasv for its object to provide an improvedarrangement vwhereby a` predeter- 5 mined succession of signals may beautomatically and repeatedly generated by apparatus not involving theuse of mechanically moving parts. 'I'hough not limited exclusively tokthe uses herein mentioned, the invention is particularly applicable tonavigation aiding wireless transmitting systems yof the kind whereininterlocking or co-operating signals (such as the Morse letters E and T)are alternately transmitted in directions which overlap so that areceiver situated in the roverlapping zone will receive a third signalwhich, in the case where the inter- .locking signals are the Morseletters E and T, should be a continuousv dash. With the aid of such atransmitting system a mobile receiving station, for example an aircraftequipped with a 'wireless receiver, may be navigated in a predeter-@minedfdirection since so long as it is within the "area of overlap thecharacteristic signal made up4 of the two interlocln'ng or co-operatingsignals will be received.

Hitherto in transmitting systems of the nature v 'of the interlockingsignal system just described, the necessary signals have been usuallyobtained by means of keys, switches, electromagnetic relays, and similardevices.

k.One objection to the use for suchpurposes of "keysyswitches or relayshaving mechanically moving parts is that if Vthe keying mechanism 'hasappreciable transit time, this transit time gives rise to intervalsbetween the interlocking signals and accordingly. if such intervals arepresent, a receiver in the overlap zone will not 'receive (assuming thecase where the interlock- -ing signals are the Morse letters E and T) acontinuous dash but in fact will receive a dash which is more or lessbroken up into a succession of signals. This breaking up kmakes ity'diflicult for the pilot at the receiver to direct his courseaccurately. If, on the other hand, 45'the signals are too clear cut, aswould rbe the vcaseif therek were employed keys or switches having zerotransit time, harmonics of the interlocking signal frequencies areapt tobe set up at the beginning and end of each of the interlocking signals(in other words key clicks occur) and this may interfere with stationsoperating on adjacent wave lengths especially if long wavesare employed.

' lAs willbe seen lter the present inventiony y55 provides an improved.automatic signal generatabove mentioned.

ing system whereby a predetermined succession of signals is repeatedlyand automatically generated. Such a system involves no mechanicallymoving parts and avoids the diiculties According to this invention anautomatic signal generating system for generating repeated successionsof predetermined signals comprises two electronic or ionic dischargepaths each including acontrol electrode, means for interconheating saidpaths so that together they possess `two states f of equilibrium andtime control means actuated by each path whereby when .one state ofequilibrium has been maintained for a predetermined period of time thesaid state is disturbed and the second state of equilibrium assumed, thesecond state of equilibrium being in turn automatically disturbed afterthe lapse of a second predetermined period of time to reinstate theiirstr state.

The invention is illustrated in the accompanying diagrammatic drawing inwhich Fig. l shows a multivibrator in combination with gaseous dischargetube means for iixing the time constants;

Fig. 2 shows a modification including the addition of other elements;and

Fig. 3 shows an exemplary circuit in which the invention may be founduseful.

Referring to Fig. 1 which shows one way of carrying out this invention,two triode valve discharge paths are employed. For simplicity ofdescription it will be assumed that the arrangement now to be describedand illustrated comprises two independent triodes I, 2, having theircathodes 3, 4, connected together, but it is to be understood that, ifdesired, the two triode discharge paths may have a common cathode and`be constituted by suitably disposed electrodes arranged in a singleenvelope. In the specified embodiment illustrated the anode 5 of thetriodel I is cross connected to the grid 6 of the triode 2 through asuitable resistance l the grid end of which is earthed through a gridresistance 8. vSimilarly the anode 9 of the 45 triode 2 iscross-connected to the grid I0 of the triode I through ar suitableresistance II the tive terminal v,I5 connected to earth and its Apos- 55itive terminal I 6 connected to the two anodes 5, 9, each anodeconnection containing a suitable resistance I1 or I8. Each anode is alsoconnected to earth through a circuit including a. resistance I9 or 20 inseries with a condenser 2| or 22, the condenser in each case being uponthe earth side. The junction point of each of said resistances I9 or 20with the appropriate condenser 2| or 2'2 is connected to the grid Il) or6 of the appropriate Valve I or 2 through a glow discharge device 23 or24 in series with a resistance 25 or 26. The triodes may be of theindirectly heated-i cathode type as shown, in which case the heaters 2l,28, may be energized with raw alternating current through a transformer29 or in any other convenient way.

It will be seen that with this arrangement the anodes and grids arecross-connected and it will be appreciated that any increase inpotential of the anode of one valve will increase the grid potential ofthe other valve, such increase of grid potential in turn causingdecrease of, i. e. making more negative, the grid potential of said onegrid. Thus the arrangement has two states of equilibrium.

The operation is as followsz-Suppose the arrangement to be in that stateof equilibrium in which the anode 5 of they valve I is most positive.

Then when this state is established the condenser 2I will charge up at arate determined, inter alia, by its own value, and the value of theseries resistance I9 until it accumulates a charge sufficient to breakdown the glow discharge device 23. When this device 23 breaks down thereis applied to the grid Ill a pulse of sufcient magnitude to disturb thestate of equilibrium and cause the whole arrangementto swing over almostinstantaneously to its other state of equilibrium. The arrangement willremain in the said other state of equilibrium until the glow dischargedevice 24 in the grid circuit of the second valve 2 in turnV breaks downwhen again the arrangement will swing over to its iirst state ofequilibrium. By suitably choosing the magnitudes of the components eachstate of equilibrium may be arranged to be maintained for a desiredpredetermined time; for example, one state of equilibrium may bearranged to be maintained for a-period equivalent to a Morse dot and theother for a period equivalent to a Morse dash so that signalscorresponding to the Morse letters E and T will be successively andrepeatedly generated.

An arrangement as above described may beemployed to control aninterlocking signal type of navigation aiding transmitting station inany convenient way so that one of the two interlocking signals is sentin one of the two overlapping directions while the arrangement is in onestate of equilibrium and the other is sent in the other direction whilethe said arrangement is in its other state of equilibrium. For example,the potential changes set up between the anode 5 of the iirst valve Iand earth may be applied to the screen grid or anode of a Valve (notshown) suitably connected in the transmitting station (not shown) tocontrol transmission in one direction, while the potential changes setup between the anode 9 of the second valve 2 and earth may be similarlyapplied to the screen grid or anode of a valve suitably connected in thetransmitting station to control transmission in the second of the twooverlappingdirections. 'I'hus the anode of one valve in the arrangementabove described may be regarded asan outputterminal for one signal andthe anode of the other valve may be regarded as the output terminal forthe other. The actual output terminals are shown at 30.

It is not necessary in carrying out this invention that the dischargepaths be of the hard valve type, for mercury vapor or other gas lledvalves may be used. Where, however, valves having a considerable gaslling are employed, that is to say where so-called gas relays are used,it should be remembered that such valves cannot be renderednon-conductive (once they have become conductive) merely by changing thecontrol grid voltage, for, as is well known, once a device of this typepasses anode current its anode voltage must be reduced substantially tozero before it can be switched out.

'I'here is also a critical value of grid bias at which a device of thekind in question will begin to conduct after having been non-conductive,this critical value being almost an inverse rectilinear function of theanode voltage. Accordingly, where gas relays are to be employed in anarrangement as illustrated'in Fig. l the said arrangement should bemodied by including a condenser of suitable size directlyinterconnecting the anodes of the two relays, i. e. by providing aninter-anode condenser. Such a condenser is shown at 3| in Fig. 1. Thus,assuming the potential of the anode of the relay I is high and that ofthe anode of the relay 2 low, this condenser 3I will be charged with itsterminal adjacent the i..

anode of the relay I at a high potential and its other terminal at a lowpotential. If now the grid of the relay I is impulsed positively by thebreak down of the discharge device in its circuit and if theinstantaneous value of this positive impulse is more than the criticalvalue for the gas relay in question, the relay I will become conductive,the voltage on its anode relative to its cathode will fall to a lowvalue (corresponding to the ionization potential of the gas filling).and that terminal of theinter-anode condenser 3| adjacent the anode ofrelay 2 will drop below cathode potential causing the second relay 2 tobecome non-conductive, whereupon the said inter-anode condenser 3I willbegin to charge in the opposite direction.

If desired, the resistance I4 may be shunted by a suitable condenser soas to produce a steadying action and, of course, if desired, the saidresistance may be replaced by a grid bias battery or the like.

In arrangements wherein gas filled triodes are employed it may occurthat, upon initially switching on, both triodes conduct, neithercondenser receiving a sufficient charge to break down its dischargedevice and impulse the other grid; this state of affairs corresponds toa third or intermediate state of equilibrium. To overcome this acondenser 32 may be arranged to charge through a resistance 33 from thepotential diference across one anode resistance (preferably the onecorresponding to the shorter signal) the condenser 32 being connected onthe anode side and having associated therewith an auxiliary neon orother discharge device -34 arranged so that when discharge takes placein the auxiliary device 34 the positive terminal of the said condenser32 is instantly connected to a point of zero or low potential so thatthe potential of the anode 5 is depressed below zero and the dischargein the gas filled triode I extinguished. The time constant of theresistance capacity comblnation 32, 33, is'made so long that when thewhole arrangement is in normal operation (i. e. afterstarting).theicondenser 32 neveracquires a suicient-'charge to `causethe-auxiliary discharge l device 34 to break down. This "self-starting:rangement takes up normal operation.

arrangement 32, 33, 34 is a reiinement which,

Y though available for use, is not essential. In prac- -vtice with anarrangement as shown in Fig. 1 and utilizing gas filled relays it hasbeen found that,

although both gas iilled relays conduct if the anodes are switched onbefore the cathodes reach operating temperature (the worst case) theanode currents rare not equal and one timing condenser (2| or 22) doesreceive a sufficient charge to break down the associated device 23 or24. Frequently this rst discharge is insuiiicient to extinguish theother relay and two or three discharges may take place before the wholear- From the practical view point, this false action when rst startingup is of `negligible importance.

In some cases it may be desired to provide for possible inequalities ormanufacturing inaccuracies in the valves or other components employed.This may be provided for in various ways; e. g. in a circuit as shown inFig. 1 the various yresistances may be made variable, or alternatively,instead of connecting the screen rgrids of the valves in the transmitterto be controlled to the anodes of the valves or relays 2 (ashereinbefore described) the said screen grids Y maybe connected totapping points, which may be adjustable, on the anode resistances |1 andI8.

lFig. 2 shows a somewhat improved arrangement which provides for a morecomplete discharging of the timing condensers 2|, 22 than is obtainedwith the circuit of Fig. 1. The circuit arrangement of Fig. 2 includes apair of electron discharge tubes and 2, gaseous discharge tubes 23 and24 connected to the grids of the respective tubes in the same manner asshown in Fig. 1, timing circuits |92| and 20--22 the same as shown inFig. 1 and resistive cross-connections and 1 between the anode of onetube and the control grid of the other tube. The principal difierencebetween Figs. 1 and 2 is that in the latter figure each timing condenser2| or 22 is associated with a high vacuum valve 35 or 36 having itscathode 31 or 38 connected to the low voltage side of the appropriatecondenser 2| or 22 and its anode 39 or 40 connected to the high voltageside of the said condenser. 'Ihe grids 4|, 42 are connected to pointsintermediate the resistors Il and 1 respectively and also to biasingresistors I2 and 8 respectively, the latter being grounded.

' This arrangement is such that while relay I has its grid negative andits timing condenser 2| charging, valve 35-which is across condenser2|-has its grid biased beyond cut-oil for the highest anode voltage thesaid valve 35 can receive, which voltage is, of course, determined bythe breakdown voltage of the device 23. Since, in these circumstances,valve 35 is non-conductive, it does not interfere with the charging ofcondenser 2|. When, however, device 23 breaks down and relay becomesconductive the grid bias on valve 35 is automatically reduced so that itbecomes conductive and thus gives a more complete discharge of condenser2|. A similar action takes place as regards the valve 36. There arecertain other minor differences between Figs. 1 and 2, as will beobvious from the drawing. I3 is a jack for test purposes.

If in any case it be desired to lock an arrangement as hereinbeforedescribed in one of its positions of requilibrium (e. g. for testpurposes) this may conveniently be done by disconnecting either relayanode and its timing condenser and switches (not shown) may be providedfor this purpose.

If, in Fig. 2, the triodes 35, 36 be removed the arrangement startsslowly from cold but speeds up during the rst few reversals until alimiting' speed is attained and the timing may not be perfectly regular.In this condition the variations in characteristics betweenindividualdevices 23, 24, (these variations may be appreciable) will have moreeffect on the circuit than is the case where the valves 35, 36, areemployed. In place vof using valves 35, 36 to assist dischargeelectromagnetic or other relays may be employed as will be apparent tothose skilled in the art.

Fig. 3 shows one form of circuit suitable for use under the control ofarrangements as hereinbefore described. The entire circuit arrangementas shown, except for the tubes and 2, may be considered as a workcircuit to be inserted between the terminals 30 of Fig. l. In otherwords, the resistor 43 has one of its terminals direct-connected to theanode 5 of the tube through the conductor 30 on the left side of Fig. 1,while resistor 46 has a corresponding connection through the right handconductor 3D to the anode 9 of the tube 2. The anode 5 of relay l isconnected through resistance 43 to the middle grid 44 of a pentode 45and a similar connection is made through a resistance 46 from the anode9 to the middle grid 41 of a second pentode 48. The cathodes of thepentodes are connected to one another and to the positive terminal of asuitable potential source 49 (e. g. of 80-100 volts) through automaticbiasing resistance-capacity combinations 5|), 5|. The outer orsuppressor grids of the pentodes are connected to the cathodes as in theusual way and the high frequency input is applied to the control grids52, 53 in parallel from terminals 54 as shown.

Anode potential is applied to the anodes 55, 56 as indicated and eachanode is connected through a condenser 51 or 58 to one or other end of atuned circuit 59. Condensers 60, 6|, are connected between the screengrids 44, 41 and earth as shown.

When relay is non-conductive anode 5 is at high potential and screengrid 44 at substantially the same potential, screen grid 41 being atthis instant at low potential. Accordingly, for these conditions, tunedcircuit 59 is eiectively operated by condenser 51. When the potentialsof anodes 5 and 9 reverse, the tuned circuit will be effectivelyoperated by condenser 58. Since the grids 52, 53 are connected to thesame point the result of causing the tuned circuit 59 to be excitedalternately at opposite ends is to cause the high frequency transmittedto be reversed in phase.

The purpose of the source 49 is to ensure that the screen grid of thatpentode which is for the moment idle, is brought approximately to earthpotential. The resistance condenser combination 43, 60 and 46, 6Idetermine the rapidity with which the screen grids 44, 41 can assumechanged potentials (under the control of the anodes 5, 9) and bysuitably adjusting their values key clicks can be substantially avoided.

The invention is of general application to all cases where automaticsignal control is desired e. g. it may be used to control automatictraiiic light or signal apparatus.

I claim:

1. An automatic signal generating system for generating repeatedsuccessions of predetermined signals comprising two electron dischargetubes each including at least three electrodes, means includingcross-connections between an input electrode of each tube and an outputelectrode of the other tube respectively for enabling said tubes toassume different degrees of conductivity sequentially, and time controlmeans including gas filled discharge tubes each gas lled tube beingconnected in series between the control electrode of one of the firstsaid tubes and a resistive connection to the anode of the same one ofthe rst said tubes whereby when one state of conductivity has beenmaintained fora predetermined period of time the said state is disturbedand the second state'of conductivity assumed, the second state ofconductivity being in turn automatically disturbed after the lapse of asecond predetermined period of time to re-instate the rst state.

2. An automatic signal generating system for generating repeatedsuccessions of predetermined signals comprising two electron dischargetubes having interconnected cathodes, each tube including a controlelectrode and an anode, a conductive impedance connected between theanode of each tube and the control electrode of the other, a pair ofcircuits each including a resistance in series with a timing condenserconnected across between they anode and cathode of the respective tubes,a circuit including a gaseous discharge device connected between eachsaid control electrode and the high potential side of one of said timingcondensers respectively, and means for causing the two first saidtubes'to alternately assume different states of conductivity each ofwhich is disturbed after having been maintained for a predeterminedtime, by a ow of spacecurrent ,in a respective one of said gaseousdischarge tubes, and means for taking oi generated signals from theanode circuits of the rst said discharge tubes.

3. A vibrating system comprising a pair of electron discharge tubes,each tube containing a cathode, an anode, and at least one grid, aresistive connection between the anode of each tube and the grid of theother tube, two circuits each including a gaseous discharge tube and aresistor., each said circuit interconnecting an anode and a grid commonto a respective one of said tubes, two capacitive circuits each couplingthe cathodes of said tubes to respective points on the said circuitsintermediate the gaseous discharge tube and the resistor, and means forcausing said discharge tubes toalternately assume diierent degrees ofconductivity, the periodicity of alternations being determined by thetime constants of said resistors and said capacitors.

4. A system in accordance with claim 3 and having two auxiliary electrondischarge tubes the discharge path in each of which is in shunt with agiven capacitor respectively in said two capacitive circuits.

NEWSOME HENRY CLOUGH.

